Cellular wireless networks such as a UMTS Terrestrial Radio Access Network (UTRAN) and an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), deploy cells capable of covering different size areas to improve cell coverage or to enhance throughput. Small cells (e.g., pico cells, relay cells, or femto cells) cover small areas and overlay large cells (also known as macro-cells) that cover larger areas. A network including macro cells and small cells is referred to as a heterogeneous wireless communication network or, for simplicity, as a heterogeneous network.
Macro-cells and small cells may operate in the same or different carrier frequencies. Operating the macro-cells and small cells on the same frequency generates cell splitting gain and, thus, increases system capacity. On the other hand, operating the macro-cells and small cells on the same carrier frequency increases the interference among cells.